Interest in dendritic compounds has grown in recent times, and dendrimers have found application in a wide range of areas, such as pharmaceuticals, drug delivery, gene delivery, sensor technologies (cation photodetection and fluorescence signal quenching), in the synthesis of monodisperse metallic nanoparticles, in environmental remediation, as blood substitutes usually in the oxygen-carrying sense (oxygen therapeutics) and plasma substitutes (volume expenders).
Dendritic structures tend to be complex. However, for some applications, such as pharmaceuticals, it is desirable to employ compounds that are discrete, well-characterised, single entities. This can be an issue in the dendrimer space, so it is desirable to use intermediates and processes which produce such single entities. There is therefore a need for simple dendritic cores that can be used to prepare dendritic compounds for use in certain applications.
Newkome et al. (Macromolecules, 1993, 26, 2394-2396) have described the synthesis of a dodecaacid dendritic core, starting from the tetraacid compound (structure shown in Scheme 1, below) and coupling this with a branched amine. This produced a compound with twelve terminal acids (attachment points), which was further elaborated (through five generations) to produce dendrimers having up to 972 terminal acids.
Newkome et al. (J. Org. Chem. 2002, 67, 3957-3960) have also reported the synthesis of a tetraamine (amine terminated) dendritic core, starting from the tetraacid compound. The tetraamine core was further elaborated by reaction with excess acrylonitrile to generate an octanitrile as an oily product.
Hukkamäki et al. (Hukkämaki, J.; Pakkanen, T. T. Journal of Molecular Catalysis A: Chemical 2001, 174, 205-21,) have also described the synthesis of the same amine terminated dendritic core. The tetraamine core was further elaborated by reaction with acrylonitrile to produce a (two generation) dendrimer having eight terminal amine groups.
For the synthesis of simple, well-defined dendritic molecules as single compounds, it would be desirable to employ a simple, stable dendritic core as an intermediate which could provide a route to the synthesis of, for example, dendrimers having pharmaceutical uses.
It is therefore an object of the present invention to provide intermediate compounds for the preparation of dendritic compounds, or to at least provide a useful choice.